AB0826 EXPLORING THE POTENTIAL GENDER DIFFERENCE IN MYOSITIS: DISEASE PHENOTYPE AND ANTIBODY PROFILE FROM A SINGLE-CENTER ITALIAN COHORT
Authors: E. Cela, P. Triggianese, B. Kroegler, A. D’antonio, P. Conigliaro, S. Modica, E. Greco, A. Bergamini, M. S. Chimenti
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Idiopathic inflammatory myopathies (IMM) include a heterogeneous group of rare autoimmune diseases with a large spectrum of muscular and systemic manifestations, mainly involving skin and lung <sup>[1,2]</sup>. Myositis specific antibodies (MSA) and myositis associated antibodies (MAA) have been described in IMM patients potentially correlating to disease outcome <sup>[3]</sup>. As well documented, autoimmune diseases present with a clear gender bias with a greater prevalence among women. To our knowledge, no studies has explored the potential gender difference in IIM patients. <h3>Objectives</h3> The aim of the study was to explore differences in disease features, clinical outcome, antibody profile, and treatments in IMM patients according to the gender. <h3>Methods</h3> In an observational study, we included patients with a defined IIM diagnosis who were referred to 3<sup>rd</sup> level Rheumatology Unit "Tor Vergata" University Hospital in Rome (Italy) for the past 5 yrs (to Dec 2022). Inclusion criteria were i. a defined diagnosis of dermatomyositis (DM), polymyositis (PM), and anti-synthetase syndrome (ASS), in accordance with the 2017 EULAR/ACR criteria, ii. age ≥ 18 y.o., iii. availability of medical records and consent to study. Data comprised: disease duration and diagnostic delay, clinical phenotype, treatments, and autoantibodies including anti-nuclear antibodies (ANA), MSAs (anti -MDA5, -NXP2, -SAE, Mi2, -TIF1, anti-tRNA synthetase, -Jo1, -PL7, -EJ), and MAAs (anti-PM/Scl, -Ro52, -Ku, U1RNP). <h3>Results</h3> The study cohort comprised 31 patients who met the inclusion criteria, with a similar gender distribution [n= 17 (54.8%) females and n=14 (45.2%) males]. The median age at symptoms onset was similar in both groups (59±13.3 vs 58.6±12.6 yrs) while males experienced slightly longer diagnostic delay (10.7±14.4 vs 8.7±9.6 months) and disease duration (30±29 vs 21±20 months) than females (P &lt;0.05 for both). No significant difference in the distribution of IIM occurred between the two groups with a half of patients affecting mostly by DM (F 76.5% <i>vs</i> M 50%). However, both PM (F 6.5% <i>vs</i> M 21.4%) and ASS (F 6.5% vs M 28.6%) were moderately prevalent in males. Skin involvement occurred similarly in both groups while lung disease occurred about twofold in males (57.1%) than females (29.4%). Most patients in the cohort showed ANA titre≥ 1:160, with a comparable rate in females and males (64.7% vs 64.3%), and a positivity for at least one MSA and MAA. A double positivity of MSA occurred in 6.5% of the cohort, all females (MDA5/anti NXP2 and MDA5/EJ). The whole cohort had undergone steroids as 1<sup>st</sup> line therapy: as steroid-sparing agents, the main difference on treatments occurred for the mycophenolate mofetil which resulted significantly more administered in males (57.14%) than females (6%, P 0.002). Furthermore, among patients with lung involvement (n=13), the need to treat the progression of interstitial lung disease, by using the antifibrotic agent (nintetanib), resulted only in males (15%). <h3>Conclusion</h3> Our preliminary findings suggest that IMM can present a gender difference in disease outcome by showing a longer diagnostic delay and a higher respiratory involvement in male patients. These data might highlight a possible gender-oriented approach in accordance with a different disease profile and treatment strategies but require further investigations in a larger cohort. <h3>References</h3> [1]Lundberg, I. E. <i>et al.</i> 2017 European League Against Rheumatism/American College of Rheumatology classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups. <i>Ann. Rheum. Dis.</i><b>76</b>, 1955–1964 (2017). [2]Lilleker, J. B. <i>et al.</i> The EuroMyositis registry: an international collaborative tool to facilitate myositis research. <i>Ann. Rheum. Dis.</i><b>77</b>, 30–39 (2018). [3]Halilu, F. &amp; Christopher-Stine, L. Myositis-specific antibodies: Overview and clinical utilization. <i>Rheumatol. Immunol. Res.</i><b>3</b>, 1–10 (2022). <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.